IBKR has a new option, Midprice orders. “To achieve the midpoint price or better, the MidPrice order is routed to the exchange with the highest probability of filling as a Pegged-to-Midpoint order, or in the case of IEX as a Discretionary Peg (D-Peg) order. If no such exchange is available, the MidPrice order is routed as either a native or simulated Relative order.” I do not understand the difference between Pegged-to-midpoint order and relative order? Based on the definition, would a pegged-to-midpoint order the same as a limit order with the limit being the price between the bid and offer?
That's my understanding, but perhaps the idea is that by the time you set the limit price to midpoint and transmit, it could change. So this allows you to specify your intent better.
When you submit a REL limit order to ISLAND, it is my understanding that the order rolls up and down with the market. If you submit a mid-point order, it only becomes more agressive until it executes. It does not roll back with the market. Maybe with the exception of the IEX mid-point order. Does anyone know whether the IEX mid-point order rolls up and down with the market?